A machine tool is a device that machines a workpiece into a desired shape by moving a tool with respect to the workpiece. The motion accuracy of the machine tool directly relates to the accuracy of the workpiece. Therefore, so as not to machine large quantities of workpieces with poor accuracy and ship them to the market, the numerical control device has a function of monitoring positions of the respective shafts of the machine tool.
For example, in the conventional numerical control device described in Patent Literature 1 or 2, the operator designates a position monitoring point as a sequence number, a G code, or accompanying information in a machining program.